Vapor vent for centrifugal pump



Dec. 10, 1957 A. N. SZWARGULSKI ETAL 5,

VAPOR VENT FOR CENTRIFUGAL PUMP Filed March 21, 1955 IIIIIH IHEI! IIIIIIIIIIIHI" F'IG.5.

vALEX N. SZWARGULSKI CHARLES W. JEEP,JR.

INVENTOR.'

United States Patent VAPOR VENT FOR CENTRIFUGAL PUMP Alex N. Szwargulski, St. Louis, and Charles W. Jeep, Jr., Webster Groves, Mo., assignors, by mesne assignments, to ACF Industries, Incorporated, New York, N. Y., a corporation of New Jersey Application March 21, 1955, Serial No. 495,530

2 Claims. (Cl. 103-113) This invention relates to fuel systems for motor vehicles, and is mainly concerned with an improvement in rotary type pumps which will eliminate any accumulation of vapors and their interference with satisfactory operation of the pump to move the fuel from the fuel tank to the carburetor.

It is usual automotive practice to locate the fuel tank at the rear of the vehicle beneath the body. In this position it is below the level of the engine, and it is necessary to pump the fuel from the tank to the carburetor.

The present invention contemplates a fuel pump for use in such a fuel system. The pump comprises an electric motor drivingly connected to a rotary type of pump positioned in or on the fuel tank so as to be fed under a positive head of pressure corresponding to that imposed by the existing fuel level in the tank above the intake in the pump. A discharge fuel line connects the pump with the engine which, likewise, is maintained under positive pressure by the pump during operation. These positive pressures are desirable because of the vapor locking tendencies inherent in fuel systems, especially at high temperatures or low pressures, or both.

It is well understood that this problem of vapor lock can exist within any rotary type of pump at temperatures near and above the boiling point of the lighter ends in the fuel. This is likewise true of the centrifugal type to which this invention is applied. Under unfavorable temperature conditions, agitation of the fuel by the rapid rotation of the centrifugal impeller vanes releases or generates vapor bubbles adjacent and within the pump inlet and casing. When this occurs, it will be readily understood that the centrifugal forces act with much less effect upon the vapor bubbles, owing to their relative density, than upon the fuel which the pump is designed to handle. As a result, the gas bubbles accumulate to fill a substantial portion of the rotor between the vanes. This results in a large, ringshaped bubble adjacent the pump inlet obstructing the passage of liquid into the pump through the inlet, so that eventually the pump delivery fails and a condition of vapor lock obtains. This condition may be further aggravated by decreases in barometric pressures on the fuel in the fuel tank which necessarily occur at altitudes above sea level. Thus, a particular pump operating satisfactorily at certain temperatures at sea level will fail to deliver fuel and become vapor locked at much lower temperatures when higher altitudes are reached.

According to this invention, static pressures created by the dynamic forces of the pump impeller and existing in the pump casing are utilized to purge the pump of any accumulation of vapors which tend to impair pump capacity. In the modification shown in the accompanying drawings, the fluid entering the pump inlet is propelled beneath a recess in the casing which, in turn, is defined by abrupt vertically extending Walls which intercept the flow created by the impeller and divert .the fluid and any vapors into a vent passage extending outwardly from the pump inlet to a separate outlet. This separating action is ice aided by the natural tendencies of the lighter vapors to rise.

In the drawings:

Fig. 1 is an environmental view showing the location of the pump with respect to the fuel tank.

Fig. 2 is a side elevation of the pump with parts broken away to illustrate the internal construction.

Fig. 3 is a top plan view of the pump impeller casing.

Fig. 4 is a section on the line 44 of Fig. 3.

Fig. 5 is a side view of the impeller casing shown in Fig. 4.

F Fig. 6 is a view, in section, taken on the line 6-6 of Fig. 7 is a view, in section, of a modification of Fig. 4.

In Fig. 1 the fuel tank T has a tank opening 0 closed by a cover plate C. Integral with the cover plate are hanger members H which support the electric fuel pump P. On the cover plate C is an outlet connection D to which is attached the fuel line F extending to the carburetor of the engine. The pump P is connected to a source of electric power by way of the conductor E.

The inlet of the pump P is surrounded by a screen S. When the line E is energized and pump P is operating, fuel will flow from the tank T through the screen S to the inlet of the pump and be discharged through the line F to the carburetor of the motor vehicle.

Turning now to Fig. 2, the pump P has a motor casing 1 which contains an electric motor adapted for operation submerged in the fuel of the gasoline tank T. The details of the motor construction are fully described and shown in our co-pending application with Alfred C. Korte and Paul R. Larson, Serial No. 431,743, filed May 24, 1954, for Electric Fuel Pump.

The shaft 2 of the electric motor is connected in driving relation with an impeller 3 within the pump casing 8 of the centrifugal pump. An inlet throat 7 for the casing of the pump is concentrically arranged with respect to the hub of the impeller 3. A plurality of vanes 5 extend from the throat 7 in the pump casing 8 outwardly to a volute chamber 9 at the periphery of the impeller. Holes 10 in the impeller are for balancing the pressures acting on opposite sides.

Volute chamber 9 communicates With a discharge outlet 11 connecting with passage 12 which leads to the discharge connection D. A cover plate 13 forms a closure for the pump casing and discharge outlet 11. Bolts 14 serve to secure the pump casing 8, cover plate 13, and motor 1 in assembled relation. The ball-thrust bearing 4 is positioned between cover plate 13 and impeller 3 to hold the motor shaft against endwise movement.

Fig. 3 is a top plan view of the pump casing 8 with the impeller shown in phantom lines. The impeller blades 5 are curved to produce pumping action by clockwise rotation. Volute 9 increases in area in the same direction, so that fluid velocity at the periphery of the impeller is converted to pressure at the discharge opening 11.

According to the present invention, the pump casing 8 is constructed with a circular inlet throat 7 concentric with the impeller hub, and formed in part by an arcuate edge 6 of the casing 8, and in part by the arcuate edge 19 in the upper wall 16 of vent passage 20 which extends radially of the casing 8 to its periphery. Side walls 22 and 23 (Figs. 5 and 6) join with upper and lower walls 16 and 17 to enclose the passage 20, so that the casing 8 within the confines of the passage 20 has an upper wall and a lower Wall. Lower wall 17 terminates in an edge 18 forming an abrupt shoulder which at all point underlies the inner portion of the upper wall 16. The overhanging part of the wall 16 terminating at edge 19 is a shroud fully enclosing the blades 5 of the impeller 3. Y

The abrupt shoulder 18 is shaped as part of an ellipse and, as will be apparent (Figs. 3 and 4), it is located opposite one edge 6 of inlet 7 to define therewith an egg-shaped opening below this inlet. This construction provides the inlet throat 7 with a circular entrance or eye formed by edges 6 and 19 concentric to the hub of impeller 3 enclosing the vanes 5, and an outlet formed by edges 6 and 18 in casing 8 eccentric to the hub of impeller 3. During rotation of the impeller 3 the vanes progressively emerge from beneath one shoulder formed by edge 18, and progressively pass beneath the shoulder at the opposite side of this opening.

According to Fig. 7, which shows a modification, the pump casing is constructed with a top wall of uniform thickness generally sloping inwardly to a circular inlet throat 27 concentric with the hub of the impeller shown in phantom lines. Inlet throat 27 is formed in part by an arcuate opening 26 in one side of the casing 28, and in part by an arcuate opening 39 in the upper wall 36 of a vent passage 30 which extends radially of the casing to its periphery. Lower wall 27' of the passage 30 terminates in an edge 38 similar in shape to the edge 18 of Fig. 3, which edge 38 forms an abrupt shoulder and at all points underlies the inner portion of the upper wall 36. This overhanging part of the upper wall 36 which terminates in the edge 39 is a shroud fully enclosing the blades 5 of the impeller. The width of the passage 30 corresponds with the diameter of the inlet throat 7. This construction provides the inlet 27 with a circular entrance or eye defined by the edges 26 and 39 of the casing 28 concentric to the hub of the impeller 3 and enclosing vanes 5 thereof. Edges 26 and 38 in the casing 28 form an outlet from the throat 27 eccentric to the hub of impeller 3.

During operation of the pump P, fuel in the tank T enters through the screen S and passes into the intake throat 7 formed partly by the edge 6 in the upper wall of the casing 8 and partly in the upper edge 19 in the upper wall 16 of the channel 20. Vanes 5 will propel the fluid outwardly of the volute 9 to the discharge 11, which connects with fuel line F leading to the vehicle engine or carburetor. The electric power circuit for the pump P is usually interconnected With the ignition switch of the vehicle so that the pump P is in operation as soon as the ignition switch of the engine is closed. During operation of the pump P, pressure will be maintained in the discharge l1 and the fuel line F.

When pump P is operating, the rotation of impeller 3 causes a slight drop in static pressure at the inlet throat 7. If temperature and atmospheric pressure conditions are unfavorable, small bubbles of vapor will begin to appear in the throat and rotate intermittently in the direction of impeller rotation. These bubbles cannot easily escape to the tank because their buoyancy is not suflicient to overcome the adverse pressure gradient existing at this zone, or the counter-movement of the fuel.

The agitation incident to the rapid movement of the vanes on the impeller in the fuel will also release vapor from the fuel to form bubbles between the vanes. These, likewise, cannot escape through the inlet 7 for the same reason, and the counter-movement of the fuel tends to cause a vapor accumulation. When the accumulation progresses to a certain point, these vapors will form larger bubbles, and sometimes a series of bubbles of annular shape completely surrounds the intake 7. Consequently, unless the vapors can be effectively vented, a condition will exist wherein the flow of fuel through the intake 7 is completely blocked. This adverse condition is sometimes referred to as cavitation, but, regardless of terminology, the effect is to reduce pump discharge pressures.

In the present construction, vapor bubbles forming adjacent the hub and moving in the direction of rotation of the impeller will enter beneath the inner edge of the raised upper wall 16 of passage 20.

As the impeller rotates, the vanes pass sequentially under the opening formed by the edge 18 of the eccentric opening in the lower wall 17, causing some of the fuel between the vanes to be deflected upwardly against the upper wall 16 on contact with the abrupt shoulders at the edge 18. This action produces a pressure gradient favorable to flow in a direction outwardly of the passage 20. Thus, the interaction of the vanes with the shoulder at the edge 18, as they enter and leave the recess, effects agitation to separate the fluid from the vapors in a manner to aid the natural tendency of the bubbles to rise, and creates a pumping action generating a fiow velocity to carry the vapors away through the passage 20.

The modification shown in Fig. 7 operates in a wholly similar manner to that described above.

Two constructions have been described which will fulfill the objects of the present invention. It is contemplated, however, that other constructions will occur to those skilled in the art which come within the scope of the appended claims.

We claim:

1. A tank mountable fuel pump of the type having a pumping and discharge zone adapted for submerged operation comprising, in combination, a rotary impeller, vanes on said impeller, an electric motor, a driving connection between said motor and said impeller, an impeller casing enclosing the vanes on said impeller, said casing having an axial inlet and a tangential outlet, and a vapor vent passage in the form of a flattened tube extending radially from said fuel inlet and having an open- 9 ing defined by abrupt walls within said casing and formed eccentrically of and beneath one edge of said inlet at the commencement of the zone of pumping action of said impeller whereby the action of said vanes passing said opening first causes agitation to separate the vapors from the fuel and to propel the fuel outwardly of said passage to force vapors separated by said impeller through said vent passage, said vanes then acting to discharge the fuel in a bubble-free condition through said discharge zone and outlet.

2. In a device for discharging vapor-free liquid from a source of liquid, a centrifugal pump having a pumping zone and a discharge zone and comprising a pump casing having an axial inlet and a tangential outlet, an impeller rotatable in said casing to move liquid therethrough, said casing having a vent passage in the form of a flattened tube formed eccentrically of and beneath one edge of said inlet and extending radially from said inlet to communicate with a source of liquid, said passage having an opening located at the commencement of the pumping zone between said inlet and said impeller, whereby the impeller acts to first discharge vapor outwardly through said vent passage and then to discharge vapor-free fuel through said casing outlet under pressure, said vent passage being of greater width than height and diverging outwardly from said impeller, said vent passage opening having concave inner and outer lips, the inner lip being radially spaced from said outer lip to produce agitation of the fuel and separation of vapor therefrom.

References Cited in the file of this patent UNITED STATES PATENTS 1,345,895 Seguin July 6, 1920 2,292,993 Curtis Apr. 11, 1942 2,463,251 Curtis Mar 1, 1949 2,552,264 Edwards May 8, 1951 FOREIGN PATENTS 574,140 Great Britain Dec. 21, 1945 941,846 France -z Jan. 21, 1949 

